One document matched: draft-ietf-tls-ssl2-must-not-03.txt

Differences from draft-ietf-tls-ssl2-must-not-02.txt

Network Working Group                                         S. Turner 
Internet Draft                                                     IECA 
Updates: 5246, 4346, 2246 (once approved)                       T. Polk 
Intended Status: Standards Track                                   NIST 
Expires: May 29, 2011                                 November 29, 2010 
 
                                      
                        Prohibiting SSL Version 2.0 
                    draft-ietf-tls-ssl2-must-not-03.txt 

Abstract 

   This document requires that when TLS clients and servers establish 
   connections that they never negotiate the use of Secure Sockets Layer 
   (SSL) version 2.0.  This document updates the backward compatibility 
   sections found in the Transport Security Layer (TLS). 

Status of this Memo 

   This Internet-Draft is submitted in full conformance with the 
   provisions of BCP 78 and BCP 79.  This document may contain material 
   from IETF Documents or IETF Contributions published or made publicly 
   available before November 10, 2008. 

   Internet-Drafts are working documents of the Internet Engineering 
   Task Force (IETF), its areas, and its working groups.  Note that 
   other groups may also distribute working documents as Internet- 
   Drafts. 

   Internet-Drafts are draft documents valid for a maximum of six months 
   and may be updated, replaced, or obsoleted by other documents at any 
   time.  It is inappropriate to use Internet-Drafts as reference 
   material or to cite them other than as "work in progress." 

   The list of current Internet-Drafts can be accessed at 
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   The list of Internet-Draft Shadow Directories can be accessed at 
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   This Internet-Draft will expire on May 29, 2009. 

Copyright Notice 

   Copyright (c) 2010 IETF Trust and the persons identified as the 
   document authors. All rights reserved. 


 
 
 
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   This document is subject to BCP 78 and the IETF Trust's Legal 
   Provisions Relating to IETF Documents 
   (http://trustee.ietf.org/license-info) in effect on the date of 
   publication of this document. Please review these documents 
   carefully, as they describe your rights and restrictions with respect 
   to this document. Code Components extracted from this document must 
   include Simplified BSD License text as described in Section 4.e of 
   the Trust Legal Provisions and are provided without warranty as 
   described in the Simplified BSD License. 

1. Introduction 

   Many protocols specified in the IETF rely on Transport Layer Security 
   (TLS) [TLS1.0][TLS1.1][TLS1.2] for security services.  This is a good 
   thing, but some TLS clients and servers also support negotiating the 
   use of Secure Sockets Layer (SSL) version 2.0 [SSL2]; however, this 
   version does not provide the expected level of security. SSL version 
   2.0 has known deficiencies. This document describes those 
   deficiencies, and it requires TLS clients and servers never negotiate 
   the use of SSL version 2.0. 

   This document updates the backward compatibility sections found in 
   TLS [TLS1.0][TLS1.1][TLS1.2]. 

1.1. Requirements Terminology 

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 
   "OPTIONAL" in this document are to be interpreted as described in 
   [RFC2119]. 

2. SSL 2.0 Deficiencies 

   SSL version 2.0 [SSL2] deficiencies include: 

   o Message authentication uses MD5 [MD5].  Most security-aware users 
     have already moved away from any use of MD5 
     [I-D.turner-md5-seccon-update]. 

   o Handshake messages are not protected.  This permits a man-in-the-
     middle to trick the client into picking a weaker cipher suite than 
     they would normally choose. 

   o Message integrity and message encryption use the same key, which is 
     a problem if the client and server negotiate a weak encryption 
     algorithm. 


 
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   o Sessions can be easily terminated.  A man-in-the-middle can easily 
     insert a TCP FIN to close the session and the peer is unable to 
     determine whether or not it was a legitimate end of the session. 

3. Changes to TLS 

   Because of the deficiencies noted in the previous section: 

   o TLS clients MUST NOT negotiate or use SSL 2.0. 

   o TLS clients MUST NOT send SSL 2.0 CLIENT-HELLO messages. 

   o TLS servers MUST NOT negotiate or use SSL 2.0. 

   As described in TLSv1.2 ([TLS1.2] Appendix E.2), TLS servers that do 
   not support SSL 2.0 MAY accept version 2.0 CLIENT-HELLO messages as 
   the first message of a TLS handshake for interoperability with old 
   clients. 

4. IANA Considerations 

   None. 

5. Security Considerations 

   This entire document is about security considerations. 

6. Acknowledgements 

   The idea for this document was inspired by discussions between Peter 
   Saint Andre, Simon Josefsson, and others on the XMPP mailing list.  
   We would also like to thank Michael D'Errico, Paul Hoffman, Nikos 
   Mavrogiannopoulos, Tom Petch, Yngve Pettersen, Marsh Ray, Martin Rex, 
   and Yaron Sheffer for their reviews and comments. 

7. References 

7.1. Normative References 

   [RFC2119]        Bradner, S., "Key words for use in RFCs to Indicate 
                    Requirement Levels", BCP 14, RFC 2119, March 1997. 

   [TLS1.0]         Dierks, T., and C. Allen, "The TLS Protocol Version 
                    1.0", RFC 2246, January 1999. 

   [TLS1.1]         Dierks, T. and E. Rescorla, "The Transport Layer 
                    Security (TLS) Protocol Version 1.1", RFC 4346, 
                    April 2006. 
 
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   [TLS1.2]         Dierks, T. and E. Rescorla, "The Transport Layer 
                    Security (TLS) Protocol Version 1.2", RFC 5246, 
                    August 2008. 

7.2. Informative References 

   [MD5]            Rivest, R., "The MD5 Message-Digest Algorithm", RFC 
                    1321, April 1992.  

   [SSL2]           Hickman, Kipp, "The SSL Protocol", Netscape 
                    Communications Corp., Feb 9, 1995. 

   [I-D.turner-md5-seccon-update] Turner, S., and L. Chen, "Updated 
                    Security Considerations for the MD5 Message-Digest 
                    Algorithm", draft-turner-md5-seccon-update, work-in-
                    progress. 

 Authors' Addresses 

   Sean Turner 
   IECA, Inc. 
   3057 Nutley Street, Suite 106 
   Fairfax, VA 22031 
   USA 

   EMail: turners@ieca.com 

   Tim Polk 
   National Institute of Standards and Technology 
   100 Bureau Drive, Mail Stop 8930 
   Gaithersburg, MD 20899-8930 
   USA 

   EMail: tim.polk@nist.gov  

    












 
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